This invention relates to mercury switches in general and more particularly to a unique mercury switch configuration exhibiting a single pole triple throw operation for use in a thermostat.
The mercury switch has been widely employed as a switching element in conjunction with thermostats. Particularly, mercury switches have been employed with bimettalic type thermostats of special configuration. In such devices, the mercury switch which is a single pole, single throw element is mounted on a bimetallic spiral spring, and as the bimetallic spiral spring expands or contracts with temperature changes, the switch is tiled to close a contact and turn on a furnace or other device.
In applications where air conditioning and furnace control are required, two or more such switches are employed. Mercury switches are widely employed, as tilt switches or detectors and are capable of reliable operation, while handling relatively large currents. As such, they have been employed in many applications as they are relatively inexpensive and extremely reliable. The bimetallic spiral is also widely employed in thermostats and essentially consists of two thin strips of different metals bonded together and forming a spiral spring element. The metals undergo different amounts of thermal expansion as one metal expands more than the other during temperature changes. This causes the bimetallic element to contract and expand accordingly and hence tilt the mercury switch during temperature changes to activate a heating or air conditioning unit to maintain the monitored temperature at a desired value.
While the thermostat application of mercury switches is widespread, there are many other applications in which such switches have been employed. Due to these factors, the prior art is replete with a number of patents and devices which employ multiple contact mercury switches for various applications. However, these devices, as will be seen, are not amenable to application for thermostatic control.
U.S. Pat. No. 1,880,832 entitled MERCURY SWITCH issued on Oct. 4, 1932 and depicts a mercury switch employing a plurality of electrodes which are disposed within a mercury filled bossed recess and used to activate an electrical sign.
Other patents as U.S. Pat. No. 2,927,987 entitled LEVEL SWITCHES by H. B. Uhl issued on Mar. 8, 1962 and depicts curved envelopes which include a pluarlity of electrodes used for motor control and other applications.
Various other patents as U.S. Pat. No. 2,508,986 entitled MERCURY SWITCH by C. A. Anderson issued on May 23, 1950 and depict momentary contact mercury switches. These devices require multiple electrodes and multiple recessed housings to afford controllable operation. Other switch types and devices are shown in U.S. Pat. No. 4,138,600 and U.S. Pat. No. 2,677,031.
Essentially, upon reviewing this type of art and other patents as well, one will ascertain that the devices employ complicated housing structures for control purposes such as multiple bossed or recessedhousings as well as complicated electrode structures.
It is, therefore, an object of the present invention to provide an improved mercury switch associated with multiple electrodes which is easy to construct and is particularly adaptable for thermostat control.
A further object of this invention is to provide an improved mercury switch for use in a thermostat which switch operates as a single pole triple throw device and which is simple to use and inexpensive to construct.